In 1919, when he was 2 years old, Louis Zamperini climbed out his bedroom window and ran down the street naked. The same year, his family moved from New York to California; at one point during the trip, Zamperini went running the length of the train and right out the back of the caboose. He was later found toddling happily along the tracks.

By high school, Zamperini was a phenomenally gifted miler with astounding stamina and a hip-rolling, ground-eating seven-foot stride. But long before then, it was apparent that he had something even rarer and less easily explicable inside him: a chronic restlessness, something beyond even willpower, that wouldn't allow him to give up even when going on was no longer endurable. Zamperini's life is the subject of a new book by Laura Hillenbrand, who also wrote Seabiscuit, the story of another great racer of the 1930s. But unlike Seabiscuit's, Zamperini's story had a terrible second act that took place far from the racetrack. (See the best books of the decade.)

In 1936, Zamperini competed in the Berlin Olympics. He wasn't seasoned enough to make the U.S. team at 1,500 m, but he finished eighth in the 5,000. He wasn't that disappointed. He was only 19. He figured he'd make his mark in Tokyo in 1940. And anyway, he got to meet Hitler.

By 1940, Zamperini was closing in on a world record in the mile, but World War II beat him to the tape. The 1940 Games were canceled, and Zamperini was drafted into the Army Air Corps. On May 27, 1943, on a search mission out of Honolulu, his plane developed engine trouble and went down in the open ocean near the equator.

Zamperini and two others survived the crash and clambered onto two inflatable life rafts. By the fourth day, their food and water were gone, but Zamperini was incapable of despair. He harvested rainwater. He caught an albatross with his bare hands. He killed a shark with a screwdriver, and the men ate its liver. After 33 days, one man died. On the 40th day, Zamperini saw angels. On the 47th, they drifted into the Marshall Islands.

But his ordeal wasn't over. The islands were Japanese territory, and Zamperini was taken prisoner. He was sent to a POW camp near Tokyo, where the disciplinary officer beat and tortured him relentlessly. The man was Zamperini's natural enemy: an obvious psychopath, he lived to dominate, and Zamperini was indomitable. Their duel left Zamperini a physical wreck, on fire with dysentery and sinking fast, but now time was on his side. Japan surrendered on Sept. 2, 1945. After two years as a POW, he had survived again. (See pictures of the U.S. Marines' offensive in Afghanistan.)

It took Hillenbrand seven years to research and write Unbroken. Zamperini's story is almost dangerously rich, full of pulpy, overheated detail, but Hillenbrand cools and tempers it with precise prose and a disciplined eye for facts that ground Zamperini's incredible odyssey in reality. She notes, for instance, that by the end of their seven weeks on the ocean, dye from the rafts had turned the men a bright yellow.

Oddly, what remains a mystery at the end of Unbroken is the book's ostensible subject, the secret of Zamperini's invincible spirit. Hillenbrand wisely leaves that untouched. It's hard to imagine a psychological theory that would satisfyingly explain such an outlier. Even Zamperini, now 93, doesn't understand it: there are moments when he seems like a hostage to his own will to live, which lashes him ruthlessly onward when death would have been a relief. Shortly after his release, he told a journalist, "If I knew I had to go through those experiences again, I'd kill myself."

THis article originally appeared in the November 22, 2010 issue of TIME.